The present invention pertains to unbalance measuring and correcting methods and apparatus for rotatable bodies requiring good rotational balance. In particular, it pertains to an unbalance point measuring method and apparatus to more accurately measure unbalance points and to correct errors occurring due to deviations introduced by the measuring apparatus and/or the correction apparatus. It overcomes the errors introduced by the apparatus by using a learning process.
In the past, unbalance points have been corrected using the results of a measurement of the unbalance points of a rotatable object as corrective data. After correcting the object based on this corrective data, the corrected object was measured again and if the unbalance found in the second measurement was still greater than an acceptable preset standard value, the object was corrected again, this time using the results of the second measurement as corrective data. Again the corrected object was measured and, if necessary, the object was corrected again. This process of measuring, correcting and measuring again could be repeated many times before an acceptable level of unbalance was found. This creates a problem of low work efficiency. In this prior art process there was no learning involved. If the measuring and/or correcting apparatus was introducing a repeated error in the process, this error was merely accepted and the process repeated an unnecessarily large number of times.
Further, if the rotatable body had significant thickness, a separation would have to be made between the unbalance on one side of the body and the unbalance on the other side of the body. If this separation were made inaccurately, a problem would arise with respect to a new unbalance point created on one side due to the inaccurate correction made on the other side. U.S. Pat. Nos. 4,419,894 to Matumoto and U.S. Pat. No. 4,868,762 to Grim et al show examples of prior art unbalance measuring devices which deal with the problems of separation of two unbalance planes in a rotatable body.